In this exact form, with an acute accent on the final syllable, the headword is attested only here. To judge by the gloss (see note below), the Suda took it to be, and presented it as, an aorist participle in the neuter singular. But comparison with other lexica implies that it is, rather, a mistaken accentuation of the epic third-person plural aorist passive form tma/gen (where the accent falls on the first syllable), extracted from Homer, Iliad 16.374, they were broken off (web address 1). For the verb tmh/gw (I cut, I cleave) see LSJ s.v.
[1] The gloss comes from the verb ko/ptw (I cut off or I smite, the latter especially suggesting the use of a tool or weapon; see LSJ s.v.). For this participle see e.g. Theophrastus, On the Causes of Plants 5.11.1, of a tree that dies after having been chopped.